1. Field of the Invention
The present invention relates to a detection circuit, and more particularly, to a plug detection circuit detecting the type of earphone connected.
2. Description of the Related Art
Normally, earphones used with personal stereos are restricted to output only, but those used with cell phones can integrate microphone function. In both cases, the earphones can implement a three-wire structure. For use with a combination cell phone/PDA, however, three-wire structure is insufficient. Thus, combination cell phone/PDA units normally employ four-wire plugs. However, four-wire plugs have poor compatibility with other devices and higher cost.
Therefore, there is a need for an earphone jack that can detect the type of earphone connected that enables use thereof, irrespective of type.